Fluorescence switch for silver ion detection utilizing dimerization of DNA-Ag nanoclusters

A fluorescence switch that consists of DNA-templated silver nanoclusters (DNA-AgNCs) triggered by silver ion (Ag+) is developed to detect Ag+. The mechanism of the fluorescence switching of DNA-AgNCs is investigated by fluorescence spectroscopy, circular dichroism spectroscopy, DNA hybridization assay and mass spectrometry. Ag+ induces a dimeric structure of Cyt12-AgNCs by forming a bridge between two Cyt12-AgNCs, where Cyt12 is cytosine 12-mer; this dimer formation causes the fluorescence change of Cyt12-AgNCs from red to green. Using this Ag+-triggered fluorescence switch, we successfully detected Ag+ at concentrations as low as 10 nM. Furthermore, we quantitatively detected the Ag+ in the Silmazin®, which is dermatological burn ointment having silver sulfadiazine. Ag+ detection using this fluorescence switch has high selectivity and sensitivity, and short response time, and can be used successfully even in the presence of other metal ions.